Random access procedure timing designs

ABSTRACT

A configurable new radio (NR) RACH procedure that may be executed by a UE and a base station is disclosed. A configuration to determine, by a user equipment, a random access procedure timeline, from multiple random access procedure timelines that each define a different duration between one or more messages that are communicated in a random access procedure can be determined or transmitted. A random access preamble can be received from the UE based on the random access procedure timeline, and a response to the random access preamble can be determined or transmitted based on the random access procedure timeline.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

This application is a continuation of U.S. patent application Ser. No.16/443,429, entitled “RANDOM ACCESS PROCEDURE TIMING DESIGNS,” filed onJun. 17, 2019, which is a continuation of U.S. patent application Ser.No. 15/648,313, entitled “RANDOM ACCESS PROCEDURE TIMING DESIGNS,” filedon Jul. 12, 2017, which claims priority to U.S. Provisional ApplicationNo. 62/417,883, entitled “NEW RADIO (NR) RANDOM ACCESS PROCEDURE (RACH)TIMING DESIGNS” filed Nov. 4, 2016, which are assigned to the assigneehereof and hereby expressly incorporated by reference herein for allpurposes.

BACKGROUND

Aspects of the present disclosure relate generally to wirelesscommunication networks, and more particularly, to random access channelprocedures in a wireless communication network.

Wireless communication networks are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing the available system resources (e.g., time, frequency, andpower). Examples of such multiple-access systems include code-divisionmultiple access (CDMA) systems, time-division multiple access (TDMA)systems, frequency-division multiple access (FDMA) systems, orthogonalfrequency-division multiple access (OFDMA) systems, and single-carrierfrequency division multiple access (SC-FDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. For example, a fifth generation (5G)wireless communications technology (which can be referred to as newradio (NR)) is envisaged to expand and support diverse usage scenariosand applications with respect to current mobile network generations. Inan aspect, 5G communications technology can include: enhanced mobilebroadband addressing human-centric use cases for access to multimediacontent, services and data; ultra-reliable-low latency communications(URLLC) with certain specifications for latency and reliability; andmassive machine type communications, which can allow a very large numberof connected devices and transmission of a relatively low volume ofnon-delay-sensitive information. As the demand for mobile broadbandaccess continues to increase, however, further improvements in NRcommunications technology and beyond may be desired.

For example, for NR communications technology and beyond, current randomaccess channel procedures may not provide a desired level of speed orcustomization for efficient operation. Thus, improvements in wirelesscommunication network operations may be desired.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In an aspect, the present disclosure includes a method of wirelesscommunications including transmitting, to a user equipment, aconfiguration to determine a random access procedure timeline frommultiple random access procedure timelines that each define a differentduration between one or more messages that are communicated in a randomaccess procedure, receiving, from the user equipment, a first message ona physical random access channel, where the first message includes arandom access preamble, transmitting, to the user equipment and based onthe random access procedure timeline, a second message on a downlinkchannel in response to the first message, where the second messageincludes an uplink grant for the user equipment, receiving, from theuser equipment and based on the random access procedure timeline, arequest or indicator on an uplink channel based on the uplink grant, andtransmitting, to the user equipment, a downlink control channel for anacknowledgement message or a negative acknowledgement messagecorresponding to the request or indicator.

In another aspect, the present disclosure includes a method of wirelesscommunications that includes determining, by a processor, aconfiguration to determine, by a user equipment, a random accessprocedure timeline, from multiple random access procedure timelines thateach define a different duration between one or more messages that arecommunicated in a random access procedure, receiving, by the processorfrom the user equipment, a random access preamble based on the randomaccess procedure timeline, and determining, by the processor, a responseto the random access preamble based on the random access proceduretimeline.

In a further aspect, the present disclosure includes an apparatus forwireless communication including a transceiver, a memory configured tostore instructions, and one or more processors communicatively coupledwith the memory and the transceiver. The one or more processors areconfigured to execute the instructions to cause the apparatus totransmit, to a user equipment, a configuration to determine a randomaccess procedure timeline from multiple random access proceduretimelines that each define a different duration between one or moremessages that are communicated in a random access procedure, receive,from the user equipment, a first message on a physical random accesschannel, where the first message includes a random access preamble,transmit, to the user equipment and based on the random access proceduretimeline, a second message on a downlink channel in response to thefirst message, where the second message includes an uplink grant for theuser equipment, receive, from the user equipment and based on the randomaccess procedure timeline, a request or indicator on an uplink channelbased on the uplink grant, and transmit, to the user equipment, adownlink control channel for an acknowledgement message or a negativeacknowledgement message corresponding to the request or indicator.

In another aspect, the present disclosure includes an apparatus forwireless communication including a transceiver, a memory configured tostore instructions, and one or more processors communicatively coupledwith the memory and the transceiver. The one or more processors areconfigured to execute the instructions to cause the apparatus todetermine a configuration to determine, by a user equipment, a randomaccess procedure timeline, from multiple random access proceduretimelines that each define a different duration between one or moremessages that are communicated in a random access procedure, receive,from the user equipment, a random access preamble based on the randomaccess procedure timeline, and determine a response to the random accesspreamble based on the random access procedure timeline.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed aspects will hereinafter be described in conjunction withthe appended drawings, provided to illustrate and not to limit thedisclosed aspects, wherein like designations denote like elements, andin which:

FIG. 1 is a schematic diagram of an example of a wireless communicationnetwork including at least one user equipment (UE) having a RACHcontroller component and at least one base station having acorresponding RACH controller component, both of which can be configuredto execute a configurable new radio (NR) RACH procedure;

FIG. 2 is a state diagram of an example of possible NR radio resourcecontrol (RRC) states for a UE, in accordance with aspects describedherein;

FIG. 3 is a message flow diagram of a 4-step message flow of an exampleimplementation of a configurable NR RACH procedure, as described herein;

FIG. 4 is a portion of a RACH timeline associated with an exampleimplementation of a configurable NR RACH procedure, as described herein;

FIG. 5 is another portion of the RACH timeline associated with anexample implementation of a configurable NR RACH procedure, as describedherein;

FIG. 6 is an example of a RACH timeline associated with an exampleimplementation of a configurable NR RACH procedure, as described herein,including different optional timelines relating to successfultransmission, reception, decoding, and/or retransmissions of certainones of the messages;

FIG. 7 is a flow diagram of an example of a method of performing a NRRACH procedure where a UE can monitor a common search space for anacknowledgement (ACK) or negative ACK (NACK) corresponding to a RACHrequest;

FIG. 8 is a flow diagram of an example of a method of performing a NRRACH procedure where a UE can receive a contention resolution message inresponse to a RACH request;

FIG. 9 is a flow diagram of an example of a method of performing aconfigurable NR RACH procedure using numerology or reference timingbased on UE or base station capability information;

FIG. 10 is a flow diagram of an example of a method of performing aconfigurable NR RACH procedure based on a deployment scenario;

FIG. 11 is a flow diagram of an example of a method of performing a NRRACH procedure based on a flexible transmission indicator;

FIG. 12 is a schematic diagram of example components of a UE, inaccordance with aspects described herein; and

FIG. 13 is a schematic diagram of example components of the basestation, in accordance with aspects described herein.

DETAILED DESCRIPTION

Various aspects are now described with reference to the drawings. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofone or more aspects. It may be evident, however, that such aspect(s) maybe practiced without these specific details. Additionally, the term“component” as used herein may be one of the parts that make up asystem, may be hardware, firmware, and/or software stored on acomputer-readable medium, and may be divided into other components.

The present disclosure generally relates a configurable new radio (NR)RACH procedure that may be executed by a UE and a base station,resulting in a configurable RACH timeline that may be more efficientthan existing RACH procedures and timelines. For example, theconfigurable NR RACH procedure may utilize one of multiple possiblenumerologies (e.g., sub-carrier spacing, cyclic prefix, slot duration)and/or timing variables (e.g., timing durations or delays betweentransmission or reception of different messages) depending on one ormore of a particular use case (e.g., RRC state of UE, UE capability,base station capability, existing and/or desired numerology, existingand/or desired latency) and/or a particular deployment case (e.g.,carrier frequency utilized, cell size). Further, the present disclosuremay include additional features, such as use of a common search space ofa physical downlink channel for exchanging control information and/ormessage acknowledgements, or such as the use of known reference timingto account for misalignment or delays in message transmission, tofurther enhance the configurable NR RACH procedure.

Additional features of the present aspects are described in more detailbelow with respect to FIGS. 1-13.

It should be noted that the techniques described herein may be used forvarious wireless communication networks such as CDMA, TDMA, FDMA, OFDMA,SC-FDMA, and other systems. The terms “system” and “network” are oftenused interchangeably. A CDMA system may implement a radio technologysuch as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc.CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0and A are commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856)is commonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data(HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants ofCDMA. A TDMA system may implement a radio technology such as GlobalSystem for Mobile Communications (GSM). An OFDMA system may implement aradio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA(E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal MobileTelecommunication System (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA,E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from anorganization named “3rd Generation Partnership Project” (3GPP). CDMA2000and UMB are described in documents from an organization named “3rdGeneration Partnership Project 2” (3GPP2). The techniques describedherein may be used for the systems and radio technologies mentionedabove as well as other systems and radio technologies, includingcellular (e.g., LTE) communications over a shared radio frequencyspectrum band. The description below, however, describes an LTE/LTE-Asystem for purposes of example, and LTE terminology is used in much ofthe description below, although the techniques are applicable beyondLTE/LTE-A applications (e.g., to 5G networks or other next generationcommunication systems).

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in other examples.

Referring to FIG. 1, in accordance with various aspects of the presentdisclosure, an example wireless communication network 100 includes atleast one UE 110 with a modem 140 having a random access channel (RACH)controller component 150 that manages execution of a configurable newradio (NR; also referred to as 5G) RACH procedure 152, in communicationwith base station 105, resulting in one or more RACH timelines (e.g., aduration of one or more portions of NR RACH procedure 152) that may bemore efficient (e.g., shorter in time) than prior RACH procedures (e.g.,in LTE or 3G). For example, NR RACH procedure 152 may be configured withone or more different timing variables 154, or one or more differentsets of timing variables 154, which are capable of altering RACHtimeline. RACH controller component 150 may utilize the one or moredifferent timing variables 154, or one or more different sets of timingvariables 154, based on one or any combination of UE capabilityinformation 156, base station capability information 176, the given usecase, or the given deployment case, as will be discussed below in moredetail.

Further, wireless communication network 100 includes at least one basestation 105 with a modem 160 having a RACH controller component 170 thatmanages execution of configurable NR RACH procedure 152, incommunication with UE 110, resulting in a given one of the one or moreRACH timelines. RACH controller component 170, independently or incombination with RACH controller component 150 of UE 110, may utilizethe one or more different timing variables 154, or one or more differentsets of timing variables 154, based on one or any combination of UEcapability information 156, base station capability information 176, thegiven use case, or the given deployment case, as will be discussed belowin more detail. Thus, according to the present disclosure, NR RACHprocedure 152 may be configured in a manner that improves an efficiencyof UE 110 in randomly accessing base station 105 and establishing acommunication connection.

The wireless communication network 100 may include one or more basestations 105, one or more UEs 110, and a core network 115. The corenetwork 115 may provide user authentication, access authorization,tracking, internet protocol (IP) connectivity, and other access,routing, or mobility functions. The base stations 105 may interface withthe core network 115 through backhaul links 120 (e.g., Si, etc.). Thebase stations 105 may perform radio configuration and scheduling forcommunication with the UEs 110, or may operate under the control of abase station controller (not shown). In various examples, the basestations 105 may communicate, either directly or indirectly (e.g.,through core network 115), with one another over backhaul links 125(e.g., X1, etc.), which may be wired or wireless communication links.

The base stations 105 may wirelessly communicate with the UEs 110 viaone or more base station antennas. Each of the base stations 105 mayprovide communication coverage for a respective geographic coverage area130. In some examples, base stations 105 may be referred to as a basetransceiver station, a radio base station, an access point, an accessnode, a radio transceiver, a NodeB, eNodeB (eNB), gNB, Home NodeB, aHome eNodeB, a relay, or some other suitable terminology. The geographiccoverage area 130 for a base station 105 may be divided into sectors orcells making up only a portion of the coverage area (not shown). Thewireless communication network 100 may include base stations 105 ofdifferent types (e.g., macro base stations or small cell base stations,described below). Additionally, the plurality of base stations 105 mayoperate according to different ones of a plurality of communicationtechnologies (e.g., 5G (New Radio or “NR”), fourth generation (4G)/LTE,3G, Wi-Fi, Bluetooth, etc.), and thus there may be overlappinggeographic coverage areas 130 for different communication technologies.

In some examples, the wireless communication network 100 may be orinclude one or any combination of communication technologies, includinga NR or 5G technology, a Long Term Evolution (LTE) or LTE-Advanced(LTE-A) or MuLTEfire technology, a Wi-Fi technology, a Bluetoothtechnology, or any other long or short range wireless communicationtechnology. In LTE/LTE-A/MuLTEfire networks, the term evolved node B(eNB) may be generally used to describe the base stations 105, while theterm UE may be generally used to describe the UEs 110. The wirelesscommunication network 100 may be a heterogeneous technology network inwhich different types of eNBs provide coverage for various geographicalregions. For example, each eNB or base station 105 may providecommunication coverage for a macro cell, a small cell, or other types ofcell. The term “cell” is a 3GPP term that can be used to describe a basestation, a carrier or component carrier associated with a base station,or a coverage area (e.g., sector, etc.) of a carrier or base station,depending on context.

A macro cell may cover a relatively large geographic area (e.g., severalkilometers in radius) and may allow unrestricted access by UEs 110 withservice subscriptions with the network provider.

A small cell may include a relative lower transmit-powered base station,as compared with a macro cell, that may operate in the same or differentfrequency bands (e.g., licensed, unlicensed, etc.) as macro cells. Smallcells may include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs 110 with servicesubscriptions with the network provider. A femto cell may also cover asmall geographic area (e.g., a home) and may provide restricted accessand/or unrestricted access by UEs 110 having an association with thefemto cell (e.g., in the restricted access case, UEs 110 in a closedsubscriber group (CSG) of the base station 105, which may include UEs110 for users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers).

The communication networks that may accommodate some of the variousdisclosed examples may be packet-based networks that operate accordingto a layered protocol stack and data in the user plane may be based onthe IP. A user plane protocol stack (e.g., packet data convergenceprotocol (PDCP), radio link control (RLC), media access control (MAC),etc.), may perform packet segmentation and reassembly to communicateover logical channels. For example, a MAC layer may perform priorityhandling and multiplexing of logical channels into transport channels.The MAC layer may also use hybrid automatic repeat/request (HARQ) toprovide retransmission at the MAC layer to improve link efficiency. Inthe control plane, the RRC protocol layer may provide establishment,configuration, and maintenance of an RRC connection between a UE 110 andthe base stations 105. The RRC protocol layer may also be used for corenetwork 115 support of radio bearers for the user plane data. At thephysical (PHY) layer, the transport channels may be mapped to physicalchannels.

The UEs 110 may be dispersed throughout the wireless communicationnetwork 100, and each UE 110 may be stationary or mobile. A UE 110 mayalso include or be referred to by those skilled in the art as a mobilestation, a subscriber station, a mobile unit, a subscriber unit, awireless unit, a remote unit, a mobile device, a wireless device, awireless communications device, a remote device, a mobile subscriberstation, an access terminal, a mobile terminal, a wireless terminal, aremote terminal, a handset, a user agent, a mobile client, a client, orsome other suitable terminology. A UE 110 may be a cellular phone, asmart phone, a personal digital assistant (PDA), a wireless modem, awireless communication device, a handheld device, a tablet computer, alaptop computer, a cordless phone, a smart watch, a wireless local loop(WLL) station, an entertainment device, a vehicular component, acustomer premises equipment (CPE), or any device capable ofcommunicating in wireless communication network 100. Additionally, a UE110 may be Internet of Things (IoT) and/or machine-to-machine (M2M) typeof device, e.g., a low power, low data rate (relative to a wirelessphone, for example) type of device, that may in some aspects communicateinfrequently with wireless communication network 100 or other UEs. A UE110 may be able to communicate with various types of base stations 105and network equipment including macro eNBs, small cell eNBs, macro gNBs,small cell gNBs, relay base stations, and the like.

UE 110 may be configured to establish one or more wireless communicationlinks 135 with one or more base stations 105. The wireless communicationlinks 135 shown in wireless communication network 100 may carry uplink(UL) transmissions from a UE 110 to a base station 105, or downlink (DL)transmissions, from a base station 105 to a UE 110. The downlinktransmissions may also be called forward link transmissions while theuplink transmissions may also be called reverse link transmissions. Eachwireless communication link 135 may include one or more carriers, whereeach carrier may be a signal made up of multiple sub-carriers (e.g.,waveform signals of different frequencies) modulated according to thevarious radio technologies described above. Each modulated signal may besent on a different sub-carrier and may carry control information (e.g.,reference signals, control channels, etc.), overhead information, userdata, etc. In an aspect, the wireless communication links 135 maytransmit bidirectional communications using frequency division duplex(FDD) (e.g., using paired spectrum resources) or time division duplex(TDD) operation (e.g., using unpaired spectrum resources). Framestructures may be defined for FDD (e.g., frame structure type 1) and TDD(e.g., frame structure type 2). Moreover, in some aspects, the wirelesscommunication links 135 may represent one or more broadcast channels.

In some aspects of the wireless communication network 100, base stations105 or UEs 110 may include multiple antennas for employing antennadiversity schemes to improve communication quality and reliabilitybetween base stations 105 and UEs 110. Additionally or alternatively,base stations 105 or UEs 110 may employ multiple input multiple output(MIMO) techniques that may take advantage of multi-path environments totransmit multiple spatial layers carrying the same or different codeddata.

Wireless communication network 100 may support operation on multiplecells or carriers, a feature which may be referred to as carrieraggregation (CA) or multi-carrier operation. A carrier may also bereferred to as a component carrier (CC), a layer, a channel, etc. Theterms “carrier,” “component carrier,” “cell,” and “channel” may be usedinterchangeably herein. A UE 110 may be configured with multipledownlink CCs and one or more uplink CCs for carrier aggregation. Carrieraggregation may be used with both FDD and TDD component carriers. Thebase stations 105 and UEs 110 may use spectrum up to Y MHz (e.g., Y=5,10, 15, or 20 MHz) bandwidth per carrier allocated in a carrieraggregation of up to a total of Yx MHz (x=number of component carriers)used for transmission in each direction. The carriers may or may not beadjacent to each other. Allocation of carriers may be asymmetric withrespect to DL and UL (e.g., more or less carriers may be allocated forDL than for UL). The component carriers may include a primary componentcarrier and one or more secondary component carriers. A primarycomponent carrier may be referred to as a primary cell (PCell) and asecondary component carrier may be referred to as a secondary cell(SCell).

The wireless communications network 100 may further include basestations 105 operating according to Wi-Fi technology, e.g., Wi-Fi accesspoints, in communication with UEs 110 operating according to Wi-Fitechnology, e.g., Wi-Fi stations (STAs) via communication links in anunlicensed frequency spectrum (e.g., 5 GHz). When communicating in anunlicensed frequency spectrum, the STAs and AP may perform a clearchannel assessment (CCA) or listen before talk (LBT) procedure prior tocommunicating in order to determine whether the channel is available.

Additionally, one or more of base stations 105 and/or UEs 110 mayoperate according to a NR or 5G technology referred to as millimeterwave (mmW or mmwave) technology. For example, mmW technology includestransmissions in mmW frequencies and/or near mmW frequencies. Extremelyhigh frequency (EHF) is part of the radio frequency (RF) in theelectromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and awavelength between 1 millimeter and 10 millimeters. Radio waves in thisband may be referred to as a millimeter wave. Near mmW may extend downto a frequency of 3 GHz with a wavelength of 100 millimeters. Forexample, the super high frequency (SHF) band extends between 3 GHz and30 GHz, and may also be referred to as centimeter wave. Communicationsusing the mmW and/or near mmW radio frequency band has extremely highpath loss and a short range. As such, base stations 105 and/or UEs 110operating according to the mmW technology may utilize beamforming intheir transmissions to compensate for the extremely high path loss andshort range.

Referring to FIG. 2, UE 110 operating in wireless communication network100 (FIG. 1) may be in one of multiple possible NR technology radioresource control (RRC) states 200, where UE 110 can utilize NR RACHprocedure 152 to move from one or more non-active states into an activestate. For example, in an aspect, each of the NR technology RRC states200 may be associated with one of an idle mode 202 of operation of UE110 or a connected mode 204 of operation of UE 110. In idle mode 202,RRC states 200 of UE 110 may include a Reachable_Idle state 206 and aPower Saving Mode 208. In connected mode 204, RRC states 200 of UE 110may include an RRC_Active state 210 and an RRC_Inactive state 212.Various conditions or characteristics associated with each state, orwith transitioning from one state to another, are listed in FIG. 2. Inan example, the configurable RACH procedures described herein (e.g., NRRACH procedure 152) may be utilized to switch the UE 110 from anRRC_Inactive state 212 or a Reachable_Idle state 206 to the RRC_Activestate 210.

Referring additionally to FIG. 3 and Table 1 (below), during operation,UE 110 may execute an implementation of NR RACH procedure 152 of thepresent disclosure, according to a 4-step NR RACH message flow 300, dueto one the occurrence of one or more RACH trigger events 310. Suitableexamples of RACH trigger event 310 may include, but are not limited to:(i) an initial access from RRC_IDLE to RRC_CONNECTED ACTIVE; (ii) DLdata arrival during RRC_IDLE or RRC_CONNECTED INACTIVE; (iii) UL dataarrival during RRC_IDLE or RRC_CONNECTED INACTIVE; (iv) a handoverduring the connected mode of operation; and (v) a connectionre-establishment.

NR RACH procedure 152 may be associated with a contention based randomaccess, or with a contention free random access. In an implementation, acontention based NR RACH procedure 152 corresponds to the following RACHtrigger events 310: an initial access from RRC_IDLE to RRC_CONNECTEDACTIVE; UL data arrival during RRC_IDLE or RRC_CONNECTED INACTIVE;and/or a connection re-establishment.

In an implementation, a contention-free NR RACH procedure 152corresponds to the following RACH trigger events 310: downlink (DL) dataarrival during RRC_IDLE or RRC_CONNECTED INACTIVE; and/or a handoverduring the connected mode of operation.

On the occurrence of one or more of the above RACH trigger events 310,the execution of NR RACH procedure 152 may include 4-step NR RACHmessage flow 300 (see FIG. 3 and Table 1), where UE 110 exchangesmessages with one or more base stations 105 to gain access to a wirelessnetwork and establish a communication connection.

TABLE 1 NR RACH procedure 152, including Messages and Message Contenttransmitted over corresponding Physical (PHY) channel(s). PHY ChannelMessage Message content PRACH Msg 1 RACH Preamble PDCCH/PDSCH Msg 2Detected RACH preamble ID, TA, TC-RNTI, backoff indicator, UL/DL grantsPUSCH Msg 3 RRC Connection request (or scheduling request and trackingarea update) PDCCH/PDSCH Msg 4 Contention resolution message

At 301, for example, UE 110 may transmit a first message (Msg 1), whichmay be referred to as a random access request message, to one or morebase stations 105 via a physical channel, such as a physical randomaccess channel (PRACH). For example, Msg 1 may include one or more of aRACH preamble and a resource requirement.

At 302, one of more of the base stations 105 may respond to Msg 1 bytransmitting a second message (Msg 2), which may be referred to as arandom access response (RAR) message, over a physical downlink controlchannel (e.g., PDCCH) and/or a physical downlink shared channel (e.g.,PDSCH). For example, Msg 2 may include one or more of a detectedpreamble identifier (ID), a timing advance (TA) value, a temporary cellradio network temporary identifier (TC-RNTI), a backoff indicator, an ULgrant, and/or a DL grant.

At 303, in response to receiving Msg 2, UE 110 transmits a third message(Msg 3), which may be an RRC connection request or a scheduling request,via a physical uplink channel (e.g., PUSCH) based on the UL grantprovided in Msg 2. In an aspect, Msg 3 may include a tracking areaupdate (TAU), such as on a periodic basis or if UE 110 moves outside ofone or more tracking areas (TAs) initially provided to UE 110 in atracking area identifier (TAI) list. Also, in some cases, Msg 3 mayinclude a connection establishment cause indicator, which can identify areason for the UE 110 request to connect to the network.

At 304, in response to receiving Msg 3, base station 105 may transmit afourth message (Msg 4), which may be referred to as a contentionresolution message, to UE 110 via a physical downlink control channel(e.g., PDCCH) and/or a physical downlink shared channel (e.g., PDSCH).For example, Msg 4 may include a cell radio network temporary identifier(C-RNTI) for UE 110 to use in subsequent communications.

In the above description, a collision scenario was not discussed but acollision between two or more UEs 110 requesting access can occur. Forinstance, two or more UEs 110 may send Msg 1 having a same RACHpreamble, since the number of RACH preambles may be limited and may berandomly selected by each UE in a contention-based NR RACH procedure152. As such, each UE can receive the same temporary C-RNTI and the sameUL grant, and thus each UE may send a similar Msg 3. In this case, basestation 105 may resolve the collision in one or more ways: (i) both Msg3 may interfere with each other, and so base station 105 may not sendMsg 4, thus each UE can retransmit Msg 1; (ii) base station 105 maysuccessfully decode only one Msg 3 and send an ACK message to that UE(e.g., as Msg 4 or a separate message); and/or (iii) base station 105may successfully decode Msg 3 from both UEs, and then send a Msg 4having a contention resolution identifier (e.g., an identifier tied toone of the UEs) to both UEs, in which case each UE can receive the Msg4, decode it, and determine if the message is intended for the given UEby successfully matching or identifying the contention resolutionidentifier. It should be noted that such a problem may not occur in acontention-free NR RACH procedure 152, as in this case base station 105can inform UE 110 of which RACH preamble to use.

Referring to FIGS. 4-6 and Table 2 (below), according to the presentaspects, UE 110 and base station 105 executing NR RACH procedure 152including the 4-step message flow 300 may result in a configurable RACHtimeline 400 that is improved (e.g., having a reduced time in one ormore of the message exchanges), for example, as compared to current RACHprocedures in LTE, due to NR RACH procedure 152 being configurable byone or more timing variables 402.

It may be desirable to reduce a duration of one of more portions of NRRACH timeline 400, as compared to prior RACH procedure durations, in oneor more situations. For example, in a situation when UE 110 initiallyattempts to access the network, it may be desirable to reduce theinitial access time. For instance, when UE 110 transitions from idlestate to active state, it may be beneficial to improve the RACH timeline400, although some applications may not require any improvement. Forinstance, UE 110 operating according to ultra-reliable low latencycommunication (URLLC) specifications can go through a standard RACHprocedure (e.g., at least based on standard RACH procedure durations),then once access is established, UE 110 can be configured to communicateaccording to URLLC standards. In another case, when UE 110 transitionsfrom an inactive state to an active state, it may be desirable toimprove the RACH timeline 400 to have the transition between inactiveand active states be more seamless.

Additionally, for example, in a situation of handover of UE 110 from aserving base station to a target base station, it may be beneficial toreduce the RACH timeline 400 (e.g., where applications support bothmobility and low latency). In such as case, then it may be important tooptimize the RACH timeline 400.

Further, for example, in a situation of UL-based mobility of UE 110, itmay be beneficial to reduce the RACH timeline 400, for instance duringhigh speed movements of UE 110 and/or during communications with a smallcell base station.

In one implementation of the present disclosure, in FIGS. 4-6, theconfigurable NR RACH procedure 152 including the 4-step message flow 300may include one or more configurable timing variables 402 (T₀, T₁, T₂,T₃, T₁′, T₂′, and T₃′) that may be associated with each of the messages.Each of timing variables 402 may be configured individually or indifferent optional sets (see Table 2; e.g., LTE_like set, enhanced set,and aggressive set). As such, execution of NR RACH procedure 152 by UE110 and base station 105 can result in different duration RACH timelines400 depending on the value of the utilized timing variables 402.

For example, UE 110 and/or base station 105 may select one of the one ormore sets (Table 2) of configurable timing variables 402 based on one ormore considerations, such as but not limited to:

-   -   (i) maintaining a same or fixed timeline for all cases; and/or    -   (ii) configuring different timelines for different cases,        including:        -   (a) different RACH timelines (e.g., including different            numerology (including, but not limited to sub-carrier            spacing, cyclic prefix, and slot duration), at least for            data and control, and/or different latency requirements, at            least for data and control) for different use cases (e.g.,            based on different users having different processing            capability; and/or based on different networks having            different processing capability); and/or        -   (b) different RACH timelines for different deployments            (e.g., based on carrier frequency, such as but not limited            to mmWave versus sub-6 GHz; and/or based on different cell            size, such as but not limited to 100 km cells, small cells,            home cells, and/or 35 km cell sizes).

Specifically, according to the present disclosure, the following timingvariables 402 may be applied to the NR RACH procedure 152 including the4-step message flow 300:

-   -   T₀ is a time delay from the RACH trigger event 310 to the        reception of Msg 1;    -   T₁ is a time delay from the Msg 1 transmission to the beginning        of a random access response (RAR) window 404, which has a time        duration of T_RAR, wherein RAR window 404 is a time window in        which Msg 2 may be transmitted and that allows base station 105        to distribute users, e.g., UEs;    -   T₂ is a minimum UE processing delay (in time) from the time the        RAR message (Msg 2) is correctly decoded to the time where Msg 3        is transmitted, and the TA received in Msg 2 is accounted for or        applied in T₂;    -   T₃ is a time duration from the time where Msg 3 is transmitted        to the time where UE starts decoding Msg 4;    -   T₁′ is a maximum UE delay (in time) from the last subframe (SF)        or slot of RAR window 404 to the SF or slot in which Msg 1 is        retransmitted (e.g., in the case where UE 110 does not receive        RAR message (Msg 2) successfully);    -   T₃′ is a maximum UE delay (in time) between Msg 3        retransmissions (e.g., HARQ round-trip-time (RTT), for example,        up to a maximum of HARQs for Msg 3 303); and    -   T₄′ is a maximum time delay between Msg 4 retransmissions.

TABLE 2 NR RACH procedure 152 Timeline Options Option T₁ T₂ T₃ T₁′ T₃′T₄′ T_(RAR) LTE_like 3 SF 6 SF - TA 4 SF 4 SF 8 SF 8 SF 10 SF timelineEnhanced 2 SF 2SF - TA 2 SF 2 SF 4 slot 4 slot 5 SF timeline Aggressive1 slot 2 slot - TA 1 slot 1 slot 2 slot 2 slot [5] slot timeline

LTE_like timeline can be based on timelines defined in 3GPP TS 36.321section 5.1.4 and TS 36.213 section 6.1.1; SF is fixed to a referenceduration; slot duration can vary dependent on numerology. T₁′ in theLTE_like set of timing variables 402 can start with default/fixednumerology then transition to different numerology during NR RACHprocedure 152. The value of T₁′ may vary depending on a number or areason for retransmission of Msg 2 302, e.g., if UE 110 could decode RARmessage (Msg 2) 302 but RAR message (Msg 2) 302 is not correct, thenT₁′=5 slots. The aggressive timeline can be used for use with small celldeployments with the highest capability base stations and the highestcapability UEs, for example, and/or for a contention-free NR RACHprocedure 152. In addition, the aggressive timeline can have NR RACHprocedure 152 following different numerology, for instance, slotduration is a function of numerology, e.g., URLLC has a slot duration of250 usec. Moreover, for example, the values of timing variables 402 foreach timeline option (e.g., LTE_like, enhanced, and aggressive) of NRRACH procedure 152, and the number of different optional sets, may varyand may be configured by each wireless communication system operatorimplementing the present disclosure.

Additionally, while FIGS. 4-6 represent one example of the varioustiming variables 402 (T₀, T₁, T₂, T₃, T₁′, T₂′, and T₃′) as beginning atthe start of an event (e.g., at the beginning of RACH trigger event 310,at the beginning of transmission of Msg 1 or Msg 3, at the beginning ofreception of Msg 2 or Msg 4), the beginning of the duration of eachtiming variable 402 may be measured from some other point in time. Forinstance, the beginning of the time period for each timing variable 402may be measured from the end of an event, or from some other point intime (middle of an event; timing offset from beginning or end of anevent) that can be associated with or determined for an event.

Additionally, referring specifically to FIG. 4, in some implementationsof the present disclosure, multiple transmissions of Msg 2 302 may bepresent within RAR window 404 (e.g., depending on networkimplementation). For instance, base station 105 may send more than oneRAR message (Msg 2) 302 per UE 110 within RAR window 404, such as forredundancy. Also, for instance, base station 105 may send different RARmessages (Msg 2) 302 for each of multiple UEs within RAR window 404,such as to enable base station 105 to serve multiple UEs. In such cases,according to one implementation of the present disclosure, UE 110 maynot combine multiple transmission occasions (e.g., multiple received Msg2s) when decoding Msg 2 302. Instead, UE 110 transmits Msg 1 301, startsto monitor RAR window 404 after T₁, and decodes Msg 2 302 successfullyif the decoded Msg 2 302 is the correct message, e.g., the Msg 2 302intended for UE 110 (and not for another UE) based on a matching RACHpreamble, and/or a first successfully decoded one of multiple redundantMsg 2s 302 transmitted to UE 110.

Referring specifically to FIG. 5, in some cases, Msg 1 301 may beretransmitted when UE 110 is unable to receive Msg 2 302 successfullywithin RAR window 404. For example, if UE 110 gets to a last SF of RARwindow 404 and is not able to successfully decode Msg 2 302, then UE 110waits T₁′ and then retransmits Msg 1 301. In an aspect, UE 110 may beconfigured (e.g., based on a specification, based on receivingconfiguration information from the network, such as in a systeminformation block (SIB) or master information block (MIB) transmitted bybase station 105, dedicated control signaling, RRC or other higher layersignaling, etc.) with a maximum number of retransmissions of Msg 1 301.Also, in some cases, UE 110 may increase a transmission power of one ormore (e.g., each) subsequent retransmission of Msg 1 301, e.g., in anattempt to enable base station 105 to better receive the message. Assuch, UE 110 may transmit one or more (e.g., each) successive Msg 1 301with power ramping (e.g., based on a valued defined by a specificationor provided by the network/base station 105). Additionally, in someaspects, the values of T₁ and T₁′ can be randomly selected or specifiedto avoid collision between different UEs.

Referring specifically to FIG. 6, according to this disclosure, inperforming NR RACH procedure 152, UE 110 and base station 105 mayutilize a common search space of a physical control channel, such as aphysical downlink control channel (PDCCH), for messaging relating tomessage flow 300. In an aspect, UE 110 may monitor a common search spaceof the PDCCH for an acknowledgement message or negative acknowledgementmessage transmitted by base station 105 and corresponding to receipt ofMsg 3 303 at base station 105. In another aspect, UE 110 may monitor acommon search space of the PDCCH for receipt of a DL grant for receivingMsg 4 304 transmitted by base station 105. In this aspect, the DL grantfor Msg 4 304 received by UE 110 on the common search space of the PDCCHmay be an alternative manner for delivering this DL grant, e.g., insteadof including this DL grant in Msg 2 302.

In operation, for example, in a first use case 601 where the DL grant isdelivered in Msg 2 302 and all messages are successfully received anddecoded, then UE 110 may not need to utilize (at least with respect toaspects relating to retransmissions of Msg 3 and Msg 4) the commonsearch space of the PDCCH. For instance, after successful transmissionof Msg 1 301 and successful reception of Msg 2 302 by UE 110, UE 110 maysuccessfully transmit Msg 3 303, e.g., on resources provided in the ULgrant received in Msg 2 302. Further, UE 110 may successfully receiveand decode Msg 4 304, e.g., on resources provided in the DL grantreceived in Msg 2 302. Thus, the timeline corresponding to first usecase 601 represents a successful timeline without any retransmissions.

Alternatively, in a second use case 602, UE 110 may monitor the commonsearch space of the PDCCH for an ACK/NACK of Msg 3 303. For instance,after successful transmission of Msg 1 301 and successful reception ofMsg 2 302 by UE 110, and after transmitting Msg 3 303, UE 110 maymonitor the common search space of the PDCCH. Specifically, UE 110 mayperform this monitoring, such as during a monitor window 612, to listenfor an acknowledgement message or negative acknowledgement messagetransmitted by base station 105, corresponding to receipt of Msg 3 303at base station 105. In an aspect, monitor window 612 may have aspecific time duration (e.g., a SF, a slot, or one or more symbols orless), known by or otherwise configured for the UE 110, beginning atsome time after transmission of Msg 3 303 (e.g., in a next SF, slot, orone or more symbols or less). For example, base station 105 may scrambleor otherwise encode the acknowledgement message or the negativeacknowledgement message with the TC-RNTI of UE 110 so that UE 110 candetermine that the message is intended for UE 110 (e.g., by descramblingthe message based on the TC-RNTI). If a negative acknowledgement messageor no acknowledgement message is received after performing thismonitoring during monitor window 612, then UE 110 may retransmit Msg 3303, for instance (e.g., after waiting a delay time, such as T₃).

In another alternative, in a third use case 603, UE 110 may monitor thecommon search space of the PDCCH for the DL grant of the resources touse for receiving Msg 304 (also referred to as Msg 4 DL grant), e.g.,when such Msg 4 DL grant is not received in Msg 2 302. For instance,after successful transmission of Msg 1 301 and successful reception ofMsg 2 302 by UE 110 (without receiving DL grant), and after transmittingMsg 3 303, UE 110 can monitor the common search space of the PDCCH inthis example. Specifically, in this example, UE 110 may perform thismonitoring, such as during a monitor window 613, for the Msg 4 DL grantfrom base station 105. For example, base station 105 may scramble orotherwise encode the DL grant (that identifies DL resources for UE 110to use for receiving Msg 4 304) with the TC-RNTI of UE 110 so that UE110 can determine that the message is intended for UE 110. In an aspect,monitor window 613 may have a specific time duration (e.g., e.g., a SF,a slot, or one or more symbols or less), known by or otherwiseconfigured for the UE 110, beginning at some time after transmission ofMsg 3 303 (e.g., in a next SF, slot, or one or more symbols or less).Upon receipt and successful decoding of the Msg 4 DL grant received inthe common search space of the PDCCH, UE 110 may transmit anacknowledgement message to base station 105 on a physical controlchannel, such as a physical uplink control channel (PUCCH). If UE 110receives but cannot successfully decode the Msg 4 DL grant, or afterperforming this monitoring during monitor window 613 without receivingthe Msg 4 DL grant, then UE 110 may transmit a negative acknowledgementmessage to base station 105 on a physical control channel, such as thePUCCH. In response to receiving the negative acknowledgement message, orno acknowledgement message, corresponding to the Msg 4 DL grant, basestation 105 may retransmit the Msg 4 DL grant in the common search spaceof the PDCCH. Additionally, in some cases, base station 105 may wait adelay time, e.g., T₄′, before retransmitting Msg 4 304.

Referring to FIG. 7, for example, a method 700 of wireless communicationin operating UE 110 according to the above-described aspects to monitora common search space of a downlink control channel for an ACK or NACKof Msg 3 303 includes one or more of the above-defined actions.

For example, at 702, method 700 includes receiving, by a user equipment,one or more parameters related to determining a configuration indicatinga random access procedure timeline. For instance, in an aspect, UE 110may execute RACH controller component 150 and/or NR RACH procedure 152to receive the one or more parameters for determining the configuration,e.g., from a specification, from a configuration stored at the UE 110,from the base station 105, etc. In one example, UE 110 can retrieve theone or more parameters (or the configuration) from memory (e.g., memory1316 in FIG. 12), or may otherwise determine the configuration based onone or more UE capability parameters stored in memory (e.g., memory1216). For example, the one or more UE capability parameters may relateto whether the UE 110 supports a self-contained slot, as describedherein, a frequency band configured for the UE 110 (e.g., by the basestation 105), a processing capability of the UE 110, a latencyrequirement of the UE 110, etc. In an example, the UE 110 may receivethe one or more parameters as part of the RACH procedure and/or maytransmit an indication of the one or more UE capability parameters tothe base station 105 as part of the RACH procedure. Thus, for example,the UE 110 may receive the one or more parameters after one or more ofthe other blocks in method 700.

In another example, UE 110 may perform a RACH procedure into the networkusing Msg 1 and Msg 2 with the fixed numerology and reference timing,described above and further herein, but then UE 110 and base station 105may update configurations for different data/control numerology and/ordifferent timeline settings (e.g., timing variables 402, e.g., T₂, T₃,T₁′, T₂′, and T₃′) for Msg 3 and Msg 4. The updated numerology and/ortiming information for Msg 3 and Msg 4 may be carried in Msg 2, forexample, and thus the UE 110 may receive the one or more parameters inMsg 2 from the base station 105 (or in other MIB and/or SIB, dedicatedcontrol signaling, RRC or other higher layer signaling, or otherconfiguration messaging, etc.). In another example, the UE 110 mayreceive the one or more parameters as base station capabilityinformation transmitted from the base station 105 to UE 110 fordetermining the numerology and/or timeline, such as via an indication inMIB and/or SIB, dedicated control signaling, RRC or other higher layersignaling, or other configuration messaging, etc. The base stationcapability information may correspond to a carrier frequency of the basestation 105, a class of the base station 105 (e.g., macrocell,femtocell, etc.), a processing capability of the base station 105 and/orcorresponding network, etc. Further, UE 110 may provide base station 105with UE capability information, such as in RRC connection setup stagemessage such as Msg 1, as described above. Accordingly, UE 110 and basestation 105 may identify a common, compatible numerology and/or timingthat may be more efficient than the fixed numerology and referencetiming based on comparing capabilities.

In one example, based on receiving the UE capability information, the UE110 can receive the configuration as instruction from the base station105 to use a different numerology or RACH timeline (e.g., in Msg 2 wherethe base station 105 receives the capability information in Msg 1). Inanother example, UE 110 may otherwise determine the numerology or RACHtimeline to use based on the UE capability information transmitted tothe base station 105 (e.g., for transmitting Msg 3 where the UEindicates capability information in Msg 1).

At 704, method 700 includes, for example, transmitting, by a userequipment in an inactive or idle state, a first message on a physicalrandom access channel, wherein the first message includes a randomaccess preamble. For instance, in an aspect, UE 110 may execute RACHcontroller component 150 and/or NR RACH procedure 152 to transmit Msg 1301 via a transmitter (e.g., transmitter 1208, FIG. 12), as describedherein.

Additionally, at 706, method 700 includes receiving, by the userequipment, a second message on a downlink channel in response to thefirst message, wherein the second message includes a temporary cellradio network temporary identifier and an uplink grant for the userequipment. For instance, in an aspect, UE 110 may execute RACHcontroller component 150 and/or NR RACH procedure 152 to receive Msg 2302 via a receiver (e.g., receiver 1206, FIG. 12), as described herein.

Further, at 708, method 700 includes transmitting, by the userequipment, a request on an uplink channel based on the uplink grant. Forinstance, in an aspect, UE 110 may execute RACH controller component 150and/or NR RACH procedure 152 to transmit Msg 3 303 via a transmitter(e.g., transmitter 1208, FIG. 12), as described herein.

Additionally, at 710, method 700 includes monitoring, by the userequipment, a common search space of a downlink control channel for anacknowledgement message or a negative acknowledgement messagecorresponding to the request and identifiable based on the temporarycell radio network temporary identifier. For instance, in an aspect, UE110 may execute RACH controller component 150 and/or NR RACH procedure152 to receive an ACK/NACK of Msg 2 302 via a receiver (e.g., receiver1206, FIG. 12) listening to a common search space of a PDCCH, asdescribed herein.

Optionally, at 712, method 700 may include retransmitting, by the userequipment, the request in response to detecting the negativeacknowledgement message corresponding to the request. For instance, inan aspect, UE 110 may execute RACH controller component 150 and/or NRRACH procedure 152 to retransmit Msg 3 303 via a transmitter (e.g.,transmitter 1208, FIG. 12), as described herein.

Referring to FIG. 8, for example, a method 800 of wireless communicationin operating UE 110 according to the above-described aspects to monitora common search space of a downlink control channel for DL grant forreceiving Msg 4 304 includes one or more of the above-defined actions.

For instance, at 802, method 800 includes transmitting, by a userequipment in an inactive or idle state, a first message on a physicalrandom access channel, wherein the first message includes a randomaccess preamble. For instance, in an aspect, UE 110 may execute RACHcontroller component 150 and/or NR RACH procedure 152 to transmit Msg 1301 via a transmitter (e.g., transmitter 1208, FIG. 12), as describedherein.

At 804, method 800 includes receiving, by the user equipment, a secondmessage on a downlink channel in response to the first message, whereinthe second message includes a temporary cell radio network temporaryidentifier and an uplink grant for the user equipment. For instance, inan aspect, UE 110 may execute RACH controller component 150 and/or NRRACH procedure 152 to receive Msg 2 302 via a receiver (e.g., receiver1206, FIG. 12), as described herein. In addition, the second message mayinclude one or more parameters or a configuration related to determiningthe RACH timeline or numerology for a remainder of the RACH procedure(e.g., for transmitting Msg 3 and Msg 4, as described above), where theone or more parameters may indicate the numerology or RACH timeline, oneor more parameters (e.g., base station capability information) fordetermining the RACH timeline or corresponding numerology, etc.

At 806, method 800 includes transmitting a request on an uplink channelbased on the uplink grant. For instance, in an aspect, UE 110 mayexecute RACH controller component 150 and/or NR RACH procedure 152 totransmit Msg 3 303 via a transmitter (e.g., transmitter 1208, FIG. 12),as described herein.

Additionally, at 808, method 800 includes monitoring, by the userequipment, a common search space of a downlink control channel for adownlink grant for receiving a contention resolution message in responseto the request. For instance, in an aspect, UE 110 may execute RACHcontroller component 150 and/or NR RACH procedure 152 to receive Msg 4DL grant via a receiver (e.g., receiver 1206, FIG. 12) listening to acommon search space of a PDCCH, as described herein.

Optionally, at 810, method 800 may further include transmitting anacknowledgement message or a negative acknowledgement message in anuplink control channel, wherein the acknowledgement message or thenegative acknowledgement message corresponds to receipt by the userequipment of the contention resolution message in response to therequest. For instance, in an aspect, UE 110 may execute RACH controllercomponent 150 and/or NR RACH procedure 152 to transmit an ACK/NACKmessage for Msg 4 304 over a PUCCH via a transmitter (e.g., transmitter1208, FIG. 12), as described herein.

According to the present aspects and as mentioned above, a timelinedesign of NR RACH procedure 152 may take into account one or more designconsiderations. For instance, in a first approach, a same RACH timelinemay be used for all cases, at least for some initial portion of NR RACHprocedure 152 (e.g., for Msg 1 and Msg 2). Though implementation of thisdesign may be less complex than other designs, the design may be limitedby the worst capability users and worst deployment scenarios (e.g., atimeline that allows for operability with low capability users and/ordeployment scenarios may hinder throughput and/or experience for highcapability users and/or deployment scenarios). Thus, in a secondapproach, UE 110 and base station 105 may be configured to supportdifferent RACH timelines for different scenarios. For instance, in afirst case, different RACH timelines may be used for different usecases, such as but not limited to: different numerology and slotduration, at least for data and control; different latency requirements,at least for data and control; different users can have differentprocessing capability; and different networks can have differentprocessing capability. Alternatively, or in addition, in a second case,different RACH timelines may be used for different deployments, such as:different carrier frequency, e.g. mmWave vs. sub-6 GHz; and differentcell size, e.g. 100 km cells vs. small cells.

For example, according to the first approach of a fixed RACH timingdesign, regardless of data/control channel numerology, UE 110 and basestation 105 may always perform NR RACH procedure 152 with the fixednumerology and reference timing. In some scenarios, UE 110 and basestation 105 may perform the entire NR RACH procedure 152 with the fixednumerology and reference timing. In other scenarios, however, UE 110 andbase station 105 may perform only a portion of NR RACH procedure 152with the fixed numerology and reference timing, and then may switch to adifferent numerology and/or timing for a remainder of NR RACH procedure152 once UE receives updated numerology and/or timing information fromthe network. For instance, UE 110 may perform a RACH procedure into thenetwork using Msg 1 and Msg 2 with the fixed numerology and referencetiming, but then UE 110 and base station 105 may have theirconfigurations updated for different data/control numerology and/ordifferent timeline settings (e.g., timing variables 402, e.g., T₂, T₃,T₁′, T₂′, and T₃′) for Msg 3 and Msg 4. The updated numerology and/ortiming information for Msg 3 and Msg 4 may be carried in Msg 2. In orderto determine the updated configuration, base station 105 may providebase station capability information to UE 110, such as via an indicationin MIB and/or SIB, dedicated control signaling, RRC or other higherlayer signaling, or other configuration messaging. Further, UE 110 mayprovide base station 105 with UE capability information, such as in RRCconnection setup stage message such as Msg 1. Accordingly, UE 110 andbase station 105 may identify a common, compatible numerology and/ortiming that may be more efficient than the fixed numerology andreference timing based on comparing capabilities. In one example, thebase station 105, based on receiving the UE capability information, caninstruct the UE 110 to use a different numerology or RACH timeline(e.g., in Msg 2 where the base station 105 receives the capabilityinformation in Msg 1). In another example, UE 110 may otherwisedetermine the numerology or RACH timeline to use based on the UEcapability information transmitted to the base station 105 (e.g., fortransmitting Msg 3 where the UE indicates capability information in Msg1).

Referring to FIG. 9, in one example of operation of UE 110 using a fixedRACH timing design, a method 900 of wireless communications performed byUE 110 includes one or more of the above-defined actions.

For instance, at 902, method 900 includes performing, by a userequipment, a first portion of a configurable random access procedurewith a base station using a fixed numerology and/or a fixed referencetiming. For instance, in an aspect, UE 110 may execute RACH controllercomponent 150 and/or NR RACH procedure 152 to transmit Msg 1 301 via atransmitter (e.g., transmitter 1208, FIG. 12) and receive Msg 2 302 viaa receiver (e.g., receiver 1206, FIG. 12).

At 904, method 900 includes receiving, by the user equipment, basestation capability information. For instance, in an aspect, UE 110 mayexecute RACH controller component 150 and/or NR RACH procedure 152 toreceive base station capability information, e.g., in a MIB and/or SIBmessage, dedicated control signaling, RRC or other higher layersignaling, or other configuration messaging, via a receiver (e.g.,receiver 1206, FIG. 12).

At 906, method 900 includes transmitting, by the user equipment, userequipment capability information. For instance, in an aspect, UE 110 mayexecute RACH controller component 150 and/or NR RACH procedure 152 totransmit UE capability information in Msg 1 301 and/or Msg 3 303 via atransmitter (e.g., transmitter 1208, FIG. 12).

Additionally, at 908, method 900 includes performing, by the userequipment, a second portion of the configurable random access procedurewith the base station using a different numerology and/or a differentreference timing based on one or both of the base station capabilityinformation and the user equipment capability information. For instance,in an aspect, UE 110 may execute RACH controller component 150 and/or NRRACH procedure 152 to transmit and/or receive subsequent messages (e.g.,any messages after Msg 1 301 or after Msg 3, depending on when UEcapability information is transmitted to base station 105). For example,the UE 110 can be configured to determine one or more parameters forperforming the configurable random access procedure (e.g., RACH timelineparameters) based on the indicated base station and/or UE capabilityinformation.

Further, for example, according to the second approach of approach of aconfigurable RACH timeline 400, the duration of RACH timeline 400 may bedifferent for different use cases or for different deployment cases(e.g., different for different indicated base station or UE capabilityinformation). In the scenario of the RACH timeline 400 being differentfor different use cases, a first case may include initially using areference numerology and/or timing variables 402, and then changing to aconfigurable numerology and/or timing variables 402. For instance, in afirst use case, before UE 110 and base station 105 exchange capabilityinformation, such as processing capability, NR RACH procedure 152, andhence the RACH timeline 400, can follow a reference numerology and/ortiming variables 402. An example of this scenario may be when UE 110performs NR RACH procedure 152 when transitioning from RRC-IDLE toRRC-CONNECTED states.

In a second use case, for example, when UE 110 and base station 105already have knowledge on data/control channel numerology, a durationand/or timing variables 402 of RACH timeline 400 depend on thenumerology configured for the data/control channel of the knownnumerology. An example of this scenario may be when UE 110 performs NRRACH procedure 152 when transitioning to the target base station 105 ina handover (HO) procedure, where the data/control channel numerology ofthe target base station 105 could be signaled to UE 110 in a HO command(e.g., transmitted by the base station 105 or the target base station tothe UE 110 instructing the UE 110 to handover to the target base stationand/or to begin one or more processes related to handing over to thetarget base station).

In the context of using different numerology and/or timing variables 402with RACH timeline 400 for different deployment cases, the RACH timeline400 may vary depending on, for instance, a frequency band ofcommunications or a cell size of a cell with which UE 110 iscommunicating, which can be determined by the UE 110 and/or base station105 or otherwise indicated in configuration information from the basestation 105, etc. Thus, for example, there may be multiple RACHtimelines 400 for each of multiple frequency bands. In an example, themultiple frequency bands and association with the RACH timelines 400 maybe configured at the UE 110, such that the UE 110 can determine a RACHtimeline 400 based on the frequency band configured for the UE 110 bythe base station 105.

For instance, in the frequency band scenario, UE 110 and base station105 may follow a first RACH timeline 400 having one set of numerologyand/or timing variables 402 for one set of frequency bands, e.g. above40 GHz, UE 110 and base station 105 may follow a second RACH timeline400 (that is different from the first RACH timeline) having another,different set of numerology and/or timing variables 402 for another setof frequency bands, e.g., lower frequency bands. It should be noted thatthere may be any number of different RACH timelines 400 andcorresponding frequency bands.

Also, for example, for the cell size scenario, UE 110 and base station105 may follow a first RACH timeline 400 having one set of numerologyand/or timing variables 402 for large cells, e.g. 100 km coverage cells,and UE 110 and base station 105 may follow a second RACH timeline 400having one set of numerology and/or timing variables 402 for other sizedcells, e.g., macro cells having less than 100 km coverage, and/or smallcells having coverage measured in 10 s of meters. For example, the UE110 can be configured with the appropriate timeline (e.g., from basestation 105) and/or parameters for determining the timeline (e.g., cellor base station class or size). Thus, for example, there may be multipleRACH timelines 400 for each of multiple cell sizes or cell classes(e.g., macrocell, femtocell, etc.). In an example, the multiple cellsizes and association with the RACH timelines 400 may be configured atthe UE 110, such that the UE 110 can determine a RACH timeline 400 basedon the determined cell size of the serving cell (or target cell in thecase of handover).

In the above-described configurable RACH timeline 400 examples, in someimplementations, UE 110 can provide a UE capability to base station 105in RACH messages, such as Msg 1 or Msg 3 in 4-step message flow 300. Inan aspect, the UE capability may include, but is not limited to, a UEprocessing capability, whether UE 110 can support a self-contained slot(e.g., a slot having both UL and DL resources such that UE 110 canreceive downlink control information and/or data and can transmit uplinkcontrol information and/or data in the same slot) or not, whether UE 110can support one or more timing variables 402, etc. After base station105 receives UE capability information from UE 110, then base station105 and UE 110 can determine a match and/or can negotiate a differentnumerology and/or timing variables 402 (as compared to a reference) toreconfigure NR RACH procedure 152 and the corresponding RACH timeline400, and thus may communicate with an enhanced processing timeline.Accordingly, procedures after the initial access by UE 110 to thenetwork can use the enhanced processing timeline, leading to reducedturn-around times.

Referring to FIG. 10, in one example of operation of UE 110 using aconfigurable RACH timing design, a method 1000 of wirelesscommunications performed by UE 110 includes one or more of theabove-defined actions.

For instance, at 1002, method 1000 includes determining, by a userequipment, one of a plurality of random access procedure timelines basedon a use case or a deployment case. For instance, in an aspect, UE 110may execute RACH controller component 150 and/or NR RACH procedure 152to determine one or more RACH timelines 400, e.g., using differentindividual or sets of timing variables 402 and/or differentnumerologies.

Additionally, at 1004, method 1000 includes performing, by the userequipment, a configurable random access procedure according to the oneof the plurality of random access procedure timelines based on the usecase or the deployment case. For instance, in an aspect, UE 110 mayexecute RACH controller component 150 to perform the configured NR RACHprocedure 152.

For example, in an aspect, the one of the plurality of random accessprocedure timelines is associated with the user equipment being in aninactive state of a connected mode, and the configurable random accessprocedure may include a current numerology associated with a basestation with which the user equipment is connected.

In another example, the one of the plurality of random access proceduretimelines 400 is associated with a handover of the user equipment to atarget base station, and the configurable random access procedure mayinclude a target numerology associated with the target base station(e.g., a numerology used by the target base station for communicatingover data and/or control channels).

In a further example, the one of the plurality of random accessprocedure timelines 400 is associated with a frequency band ofcommunications for a base station that the user equipment is attemptingto access, and the configurable random access procedure may include anumerology associated with the base station.

In still another example, the one of the plurality of random accessprocedure timelines 400 is associated with a cell size of a base stationthat the user equipment is attempting to access, and the configurablerandom access procedure may include a numerology associated with thebase station and the cell size.

For example, as described, the UE 110 can receive information regardingthe use case or deployment case, and/or the associated numerology, RACHtimeline, etc., from the base station 105. For example, UE 110 canreceive an indication of RRC state transition, handover, frequency band,cell size, etc. from the base station 105, and can accordingly determinethe RACH timeline based on one or more of these parameters. In anexample, an association of parameter values to RACH timeline can also beconfigured at the UE 110 (e.g., based on a stored configuration, aconfiguration received from base station 105, etc.), and the UE 110 candetermine the numerology, RACH timeline, or related parameters based onthe indication of RRC state transition, handover, frequency band, cellsize, etc.

Additional aspects of the present disclosure may include UE 110 and basestation 105 utilizing a reference timing in order to handle misalignmentor delay in transmission or reception of one or more of the messages ofthe 4-step message flow 300 of NR RACH procedure 152. For example, if atransmission time of one of the RACH messages is delayed, UE 110 andbase station 105 can locate a reference point, e.g., a start of a slot,to determine a reference timing for message transmission.

In another aspect, in NR RACH procedure 152, instead of having a fixedtiming for transmission of Msg 3 303, UE 110 and base station 105 canutilize an option for a flexible transmission time for Msg 3 303. Forinstance, in a case where different UEs 110 have different processingcapabilities, utilizing a flexible transmission time for Msg 3 303allows a UE with a relatively higher UE capability (e.g., relativelyfaster processing) transmit Msg 3 faster than other UEs having arelatively lower UE capability. In one implementation, base station 105may include a flexibility indication, also referred to as a requestflexible transmission indicator, in Msg 2 302. In this example, the basestation 105 may set the flexibility transmission indicator based atleast in part on determining one or more parameters related to the UE110, such as UE capability information, attainable throughput, UE class,buffer status report, etc. As such, upon receipt and decoding of Msg 2302, UE 110 may transmit Msg 3 303 at a timing based on UE capabilityand according to the request flexible transmission indicator. Moreover,when UE 110 and base station 105 are performing time division duplex(TDD) operations, the flexible transmission time for Msg 3 303 may beutilized to postpone transmission of Msg 3 303 if such transmissionconflicts with the resource scheduling (e.g., UL schedule in a slot fortransmitting Msg 3, but that slot is scheduled to be DL).

Referring to FIG. 11, in one implementation of a flexible transmissiontime for Msg 3 302, a method 1100 of wireless communications includesone or more of the above-described actions.

For instance, at 1102, method 1100 includes transmitting, by a userequipment in an inactive or idle state, a first message on a physicalrandom access channel, wherein the first message includes a randomaccess preamble. For instance, in an aspect, UE 110 may execute RACHcontroller component 150 and/or NR RACH procedure 152 to transmit Msg 1301 via a transmitter (e.g., transmitter 1208, FIG. 12), as describedherein.

At 1104, method 1100 includes receiving, by the user equipment, a secondmessage on a downlink channel in response to the first message, whereinthe second message includes a request flexible transmission indicatorand an uplink grant for the user equipment. In an aspect, the requestflexible transmission indicator comprises or indicates a delay value fordelaying the transmitting of the request. For instance, in an aspect, UE110 may execute RACH controller component 150 and/or NR RACH procedure152 to receive Msg 2 302 via a receiver (e.g., receiver 1206, FIG. 12),as described herein.

At 1106, method 1100 includes determining a conflict in a first resourcefor sending a request. For instance, in an aspect, UE 110 may executeRACH controller component 150 and/or NR RACH procedure 152 to determinea conflict, e.g., to determine that a transmission scheduled for Msg 3303 conflicts with a DL resource corresponding to the transmission.

Additionally, at 1108, method 1100 includes transmitting, by the userequipment, the request on an uplink channel based on the uplink grantand using a second resource based on the request flexible transmissionindicator. For instance, in an aspect, UE 110 may execute RACHcontroller component 150 and/or NR RACH procedure 152 to delay thetransmission of Msg 3 303 based on the conflict and further based on theflexibility for the transmission as indicated by the request flexibletransmission indicator.

Referring to FIG. 12, one example of an implementation of UE 110 mayinclude a variety of components, some of which have already beendescribed above, but including components such as one or more processors1212 and memory 1216 and transceiver 1202 in communication via one ormore buses 1244, which may operate in conjunction with modem 140 andRACH controller component 150 to enable one or more of the functionsdescribed herein related to including configurable NR RACH procedure152. Further, the one or more processors 1212, modem 140, memory 1216,transceiver 1202, RF front end 1288 and one or more antennas 1286, maybe configured to support voice and/or data calls (simultaneously ornon-simultaneously) in one or more radio access technologies.

In an aspect, the one or more processors 1212 can include a modem 140that uses one or more modem processors. The various functions related toRACH controller component 150 may be included in modem 140 and/orprocessors 1212 and, in an aspect, can be executed by a singleprocessor, while in other aspects, different ones of the functions maybe executed by a combination of two or more different processors. Forexample, in an aspect, the one or more processors 1212 may include anyone or any combination of a modem processor, or a baseband processor, ora digital signal processor, or a transmit processor, or a receiverprocessor, or a transceiver processor associated with transceiver 1202.In other aspects, some of the features of the one or more processors1212 and/or modem 140 associated with RACH controller component 150 maybe performed by transceiver 1202.

Also, memory 1216 may be configured to store data used herein and/orlocal versions of applications 1275 or RACH controller component 150and/or one or more of its subcomponents being executed by at least oneprocessor 1212. Memory 1216 can include any type of computer-readablemedium usable by a computer or at least one processor 1212, such asrandom access memory (RAM), read only memory (ROM), tapes, magneticdiscs, optical discs, volatile memory, non-volatile memory, and anycombination thereof. In an aspect, for example, memory 1216 may be anon-transitory computer-readable storage medium that stores one or morecomputer-executable codes defining RACH controller component 150 and/orone or more of its subcomponents, and/or data associated therewith, whenUE 110 is operating at least one processor 1212 to execute RACHcontroller component 150 and/or one or more of its subcomponents.

Transceiver 1202 may include at least one receiver 1206 and at least onetransmitter 1208. Receiver 1206 may include hardware, firmware, and/orsoftware code executable by a processor for receiving data, the codecomprising instructions and being stored in a memory (e.g.,computer-readable medium). Receiver 1206 may be, for example, a radiofrequency (RF) receiver. In an aspect, receiver 1206 may receive signalstransmitted by at least one base station 105. Additionally, receiver1206 may process such received signals, and also may obtain measurementsof the signals, such as, but not limited to, Ec/Io, SNR, RSRP, RSSI,etc. Transmitter 1208 may include hardware, firmware, and/or softwarecode executable by a processor for transmitting data, the codecomprising instructions and being stored in a memory (e.g.,computer-readable medium). A suitable example of transmitter 1208 mayincluding, but is not limited to, an RF transmitter.

Moreover, in an aspect, UE 110 may include RF front end 1288, which mayoperate in communication with one or more antennas 1265 and transceiver1202 for receiving and transmitting radio transmissions, for example,wireless communications transmitted by at least one base station 105 orwireless transmissions transmitted by UE 110. RF front end 1288 may beconnected to one or more antennas 1265 and can include one or morelow-noise amplifiers (LNAs) 1290, one or more switches 1292, one or morepower amplifiers (PAs) 1298, and one or more filters 1296 fortransmitting and receiving RF signals.

In an aspect, LNA 1290 can amplify a received signal at a desired outputlevel. In an aspect, each LNA 1290 may have a specified minimum andmaximum gain values. In an aspect, RF front end 1288 may use one or moreswitches 1292 to select a particular LNA 1290 and its specified gainvalue based on a desired gain value for a particular application.

Further, for example, one or more PA(s) 1298 may be used by RF front end1288 to amplify a signal for an RF output at a desired output powerlevel. In an aspect, each PA 1298 may have specified minimum and maximumgain values. In an aspect, RF front end 1288 may use one or moreswitches 1292 to select a particular PA 1298 and its specified gainvalue based on a desired gain value for a particular application.

Also, for example, one or more filters 1296 can be used by RF front end1288 to filter a received signal to obtain an input RF signal.Similarly, in an aspect, for example, a respective filter 1296 can beused to filter an output from a respective PA 1298 to produce an outputsignal for transmission. In an aspect, each filter 1296 can be connectedto a specific LNA 1290 and/or PA 1298. In an aspect, RF front end 1288can use one or more switches 1292 to select a transmit or receive pathusing a specified filter 1296, LNA 1290, and/or PA 1298, based on aconfiguration as specified by transceiver 1202 and/or processor 1212.

As such, transceiver 1202 may be configured to transmit and receivewireless signals through one or more antennas 1265 via RF front end1288. In an aspect, transceiver may be tuned to operate at specifiedfrequencies such that UE 110 can communicate with, for example, one ormore base stations 105 or one or more cells associated with one or morebase stations 105. In an aspect, for example, modem 140 can configuretransceiver 1202 to operate at a specified frequency and power levelbased on the UE configuration of the UE 110 and the communicationprotocol used by modem 140.

In an aspect, modem 140 can be a multiband-multimode modem, which canprocess digital data and communicate with transceiver 1202 such that thedigital data is sent and received using transceiver 1202. In an aspect,modem 140 can be multiband and be configured to support multiplefrequency bands for a specific communications protocol. In an aspect,modem 140 can be multimode and be configured to support multipleoperating networks and communications protocols. In an aspect, modem 140can control one or more components of UE 110 (e.g., RF front end 1288,transceiver 1202) to enable transmission and/or reception of signalsfrom the network based on a specified modem configuration. In an aspect,the modem configuration can be based on the mode of the modem and thefrequency band in use. In another aspect, the modem configuration can bebased on UE configuration information associated with UE 110 as providedby the network during cell selection and/or cell reselection.

Referring to FIG. 13, one example of an implementation of base station105 may include a variety of components, some of which have already beendescribed above, but including components such as one or more processors1312 and memory 1316 and transceiver 1302 in communication via one ormore buses 1344, which may operate in conjunction with modem 160 andRACH controller component 170 to enable one or more of the functionsdescribed herein related to including configurable NR RACH procedure152.

The transceiver 1302, receiver 1306, transmitter 1308, one or moreprocessors 1312, memory 1316, applications 1375, buses 1344, RF frontend 1388, LNAs 1390, switches 1392, filters 1396, PAs 1398, and one ormore antennas 1365 may be the same as or similar to the correspondingcomponents of UE 110, as described above, but configured or otherwiseprogrammed for base station operations as opposed to UE operations.

The above detailed description set forth above in connection with theappended drawings describes examples and does not represent the onlyexamples that may be implemented or that are within the scope of theclaims. The term “example,” when used in this description, means“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand apparatuses are shown in block diagram form in order to avoidobscuring the concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, computer-executable code or instructionsstored on a computer-readable medium, or any combination thereof.

The various illustrative blocks and components described in connectionwith the disclosure herein may be implemented or performed with aspecially-programmed device, such as but not limited to a processor, adigital signal processor (DSP), an ASIC, a FPGA or other programmablelogic device, a discrete gate or transistor logic, a discrete hardwarecomponent, or any combination thereof designed to perform the functionsdescribed herein. A specially-programmed processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aspecially-programmed processor may also be implemented as a combinationof computing devices, e.g., a combination of a DSP and a microprocessor,multiple microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on anon-transitory computer-readable medium. Other examples andimplementations are within the scope and spirit of the disclosure andappended claims. For example, due to the nature of software, functionsdescribed above can be implemented using software executed by aspecially programmed processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items prefaced by “at least one of” indicates a disjunctivelist such that, for example, a list of “at least one of A, B, or C”means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the common principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Furthermore, although elements of the describedaspects and/or embodiments may be described or claimed in the singular,the plural is contemplated unless limitation to the singular isexplicitly stated. Additionally, all or a portion of any aspect and/orembodiment may be utilized with all or a portion of any other aspectand/or embodiment, unless stated otherwise. Thus, the disclosure is notto be limited to the examples and designs described herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method of wireless communications by a basestation, comprising: transmitting, to a user equipment, a configurationto determine a random access procedure timeline from multiple randomaccess procedure timelines that each define a different duration betweenone or more messages that are communicated in a random access procedure;receiving, from the user equipment, a first message on a physical randomaccess channel, wherein the first message includes a random accesspreamble; transmitting, to the user equipment and based on the randomaccess procedure timeline, a second message on a downlink channel inresponse to the first message, wherein the second message includes anuplink grant for the user equipment; receiving, from the user equipmentand based on the random access procedure timeline, a request orindicator on an uplink channel based on the uplink grant; andtransmitting, to the user equipment, a downlink control channel for anacknowledgement message or a negative acknowledgement messagecorresponding to the request or indicator.
 2. The method of claim 1, theconfiguration being further to determine a second random accessprocedure timeline.
 3. The method of claim 2, further comprising:transmitting, to the user equipment, in a window of the second randomaccess procedure timeline and after receiving a second request orindicator, acknowledgment of the second request or indicator.
 4. Themethod of claim 3, further comprising: receiving, from the userequipment, the second request or indicator after the window responsiveto the user equipment not receiving acknowledgement in the window,without a second uplink grant after the window.
 5. The method of claim1, wherein the second message further includes a temporary cell radionetwork temporary identifier and wherein the acknowledgement message orthe negative acknowledgement message corresponding to the request orindicator is identifiable based on the temporary cell radio networktemporary identifier.
 6. The method of claim 1, the request or indicatorbeing associated with a trigger event of the random access procedure. 7.The method of claim 1, further comprising configuring, for the userequipment, a time duration for a monitor window during which to monitorthe downlink control channel for the acknowledgement message or thenegative acknowledgement message.
 8. A method of wirelesscommunications, comprising: determining, by a processor, a configurationto determine, by a user equipment, a random access procedure timeline,from multiple random access procedure timelines that each define adifferent duration between one or more messages that are communicated ina random access procedure; receiving, by the processor from the userequipment, a random access preamble based on the random access proceduretimeline; and determining, by the processor, a response to the randomaccess preamble based on the random access procedure timeline.
 9. Themethod of claim 8, the configuration being further to determine, by theuser equipment, a second random access procedure timeline, the randomaccess procedure timeline comprising a first window for the userequipment to monitor for the response to the random access preamble, andthe second random access procedure timeline comprising a second windowfor the user equipment to monitor for the response to the random accesspreamble.
 10. The method of claim 8, further comprising receiving, bythe processor and from the user equipment and based on the random accessprocedure timeline, a request or indicator on an uplink channel based onan uplink grant received by the user equipment in a second message; anddetermining, by the processor, an acknowledgement message or a negativeacknowledgement message corresponding to the request or indicator. 11.The method of claim 10, the configuration being further to determine, bythe user equipment, a second random access procedure timeline, therandom access procedure timeline comprising a first window for the userequipment to monitor for the acknowledgement message or the negativeacknowledgement message, and the second random access procedure timelinecomprising a second window for the user equipment to monitor for theacknowledgement message or the negative acknowledgement message.
 12. Themethod of claim 11, further comprising configuring, by the processor andfor the user equipment, at least one of a first duration for the firstwindow or a second duration for the second window.
 13. An apparatus forwireless communication, comprising: a transceiver; a memory configuredto store instructions; and one or more processors communicativelycoupled with the memory and the transceiver, wherein the one or moreprocessors are configured to execute the instructions to cause theapparatus to: transmit, to a user equipment, a configuration todetermine a random access procedure timeline from multiple random accessprocedure timelines that each define a different duration between one ormore messages that are communicated in a random access procedure;receive, from the user equipment, a first message on a physical randomaccess channel, wherein the first message includes a random accesspreamble; transmit, to the user equipment and based on the random accessprocedure timeline, a second message on a downlink channel in responseto the first message, wherein the second message includes an uplinkgrant for the user equipment; receive, from the user equipment and basedon the random access procedure timeline, a request or indicator on anuplink channel based on the uplink grant; and transmit, to the userequipment, a downlink control channel for an acknowledgement message ora negative acknowledgement message corresponding to the request orindicator.
 14. The apparatus of claim 13, the configuration beingfurther to determine a second random access procedure timeline.
 15. Theapparatus of claim 14, wherein the one or more processors are furtherconfigured to execute the instructions to cause the apparatus totransmit, to the user equipment, in a window of the second random accessprocedure timeline and after receiving a second request or indicator,acknowledgment of the second request or indicator.
 16. The apparatus ofclaim 15, wherein the one or more processors are further configured toexecute the instructions to cause the apparatus to receive, from theuser equipment, the second request or indicator after the windowresponsive to the user equipment not receiving acknowledgement in thewindow, without a second uplink grant after the window.
 17. Theapparatus of claim 13, wherein the second message further includes atemporary cell radio network temporary identifier and wherein theacknowledgement message or the negative acknowledgement messagecorresponding to the request or indicator is identifiable based on thetemporary cell radio network temporary identifier.
 18. The apparatus ofclaim 13, the request or indicator being associated with a trigger eventof the random access procedure.
 19. The apparatus of claim 13, whereinthe one or more processors are further configured to execute theinstructions to cause the apparatus to configure, for the userequipment, a time duration for a monitor window during which to monitorthe downlink control channel for the acknowledgement message or thenegative acknowledgement message.
 20. An apparatus for wirelesscommunication, comprising: a transceiver; a memory configured to storeinstructions; and one or more processors communicatively coupled withthe memory and the transceiver, wherein the one or more processors areconfigured to execute the instructions to cause the apparatus to:determine a configuration to determine, by a user equipment, a randomaccess procedure timeline, from multiple random access proceduretimelines that each define a different duration between one or moremessages that are communicated in a random access procedure; receive,from the user equipment, a random access preamble based on the randomaccess procedure timeline; and determine a response to the random accesspreamble based on the random access procedure timeline.
 21. Theapparatus of claim 20, the configuration being further to determine, bythe user equipment, a second random access procedure timeline, therandom access procedure timeline comprising a first window for the userequipment to monitor for the response to the random access preamble, andthe second random access procedure timeline comprising a second windowfor the user equipment to monitor for the response to the random accesspreamble.
 22. The apparatus of claim 20, wherein the one or moreprocessors are further configured to execute the instructions to causethe apparatus to receive, from the user equipment and based on therandom access procedure timeline, a request or indicator on an uplinkchannel based on an uplink grant received by the user equipment in asecond message; and determining an acknowledgement message or a negativeacknowledgement message corresponding to the request or indicator. 23.The apparatus of claim 22, the configuration being further to determine,by the user equipment, a second random access procedure timeline, therandom access procedure timeline comprising a first window for the userequipment to monitor for the acknowledgement message or the negativeacknowledgement message, and the second random access procedure timelinecomprising a second window for the user equipment to monitor for theacknowledgement message or the negative acknowledgement message.
 24. Theapparatus of claim 23, wherein the one or more processors are furtherconfigured to execute the instructions to cause the apparatus toconfigure, for the user equipment, at least one of a first duration forthe first window or a second duration for the second window.